iKenndac:
I've had my 24-105mm f/4 L since 2006, and it's been my day-to-day walkaround for most of that time. I always found it difficult to get pin-sharp shots with it, but assumed it was always my technique.

However, I recently decided to check the sharpness of my lenses and perform AFMA calibration on them. What really shocked me is that my girlfriend's EF-S 17-85mm actually appears to be sharper than my 24-105 L!

If anyone here has the 24-105 L, and have done sharpness shots with it, would you mind chipping in? I wonder if this is a naturally soft lens or if mine is out of whack. I know the lens is weakest at 24mm, but mine seems to be pretty terrible!

Standard Lightroom settings, sharpness turned down to 0.

100% crop at 105mm:

100% crop at 24mm:

Mt Spokane Photography:
Bad lenses do happen, send it to Canon for repair. There are plenty of tests and comparisons around the internet to show that it is capable of being very sharp.

I try to test any new lenses I purchase for sharpness right away. I first adjust the AFMA, and then view a variety of images to check that the lens meets expectations.

I'd find it very difficult to judge sharpness with the images you show. Their only purpose is to check for front/back focus.

Use a proper target or flat brick wall and check not only the center, but the edges and corners.

Its hard to beat the 24-105mmL for the price. You can beat it with a prime, but not a zoom in that price range.

RS2021:
From your picture, at 105mm it seems sharp enough to me for this zoom... at 24mm it looks a bit off but as noted earlier this is really not the best way to check this.

Also, take several shots at the focal lenghts and see if this is not just AF "one-off" situation. Add to this the fact, this zoom struggles in general on the wide end on both distortion and sharpness compared to sweet spots higher up in the focal length range.

If you do plan to send it to Canon...be specific to get things really looked at...just saying "I think this is soft" will generally result in them holding on to the lens for a couple of weeks, doing standard tests, and sending it back the same as you sent them with a terse note "within standard range".

24-105L from what I can tell does have some limited copy variation with some people very happy with theirs (I am one) and others really railing on it. It is also not one of those "super sharp" lenses ...if you have that expecation then it will never meet your expectations. I recently played with a friends 24-70 II and clearly the new zoom is spectacular in comparison. So, recognize the 24-105L for where it falls in the product line up...

Most happy users like me will tell you it is an awesome zoom all things considered. Love it.

tomscott:
I had the 17-85mm and it was awful.

The 24-105 is very sharp in comparison. Maybe just needs some good AFMA